Specificity exchangers are generally composed of two domains, a specificity domain and an antigenic domain. There are two general types of specificity exchangers differentiated by the nature of their specificity domains. (See e.g., U.S. patent application Ser. No. 10/372,735, hereby expressly incorporated by reference in its entirety). The first type of specificity exchanger is an antigen/antibody specificity exchanger. Several different types of antigen/antibody specificity exchangers can be made. (See e.g., U.S. Pat. Nos. 5,869,232; 6,040,137; 6,245,895; 6,417,324; 6,469,143; and U.S. application Ser. Nos. 09/839,447 and 09/839,666; and International App. Nos. PCT/SE95/00468 and PCT/IB01/00844, all of which are hereby expressly incorporated by reference in their entireties).
Antigen/antibody specificity exchangers comprise an amino acid sequence of an antibody that specifically binds to an antigen (i.e., the specificity domain) joined to an amino acid sequence to which an antibody binds (i.e., the antigenic domain). Some specificity domains of antigen/antibody specificity exchangers comprise an amino acid sequence of a complementarity determining region (CDR), are at least 5 and less than 35 amino acids in length, are specific for HIV-1 antigens, or are specific for hepatitis viral antigens. Some antigenic domains of antigen/antibody specificity exchangers comprise a peptide having an antibody-binding region of viral, bacterial, or fungal origin, are at least 5 and less than 35 amino acids in length, or contain peptides (e.g., peptides comprising epitopes) that are obtained from polio virus, measles virus, hepatitis B virus, hepatitis C virus, or HIV-1.
A second type of specificity exchanger, the ligand/receptor specificity exchanger, is also composed of a specificity domain and an antigenic domain, however, the specificity domain of the ligand/receptor specificity exchanger comprises a ligand for a receptor that is present on a pathogen, as opposed to a sequence of an antibody that binds to an antigen. That is, a ligand/receptor specificity exchanger differs from an antibody/antigen specificity exchanger in that the ligand/receptor specificity exchanger does not contain a sequence of an antibody that binds an antigen but, instead, adheres to the pathogen vis a vis ligand interaction with a receptor that is present on the pathogen. Several different types of ligand/receptor specificity exchangers can be made. (See e.g., U.S. Pat. No. 6,660,842; U.S. application Ser. No. 10/372,735; and International App. No. PCT/IB01/02327, all of which are hereby expressly incorporated by reference in their entireties).
Some specificity domains of ligand/receptor specificity exchangers comprise an amino acid sequence that is a ligand for a bacterial adhesion receptor (e.g., extracellular fibrinogen binding protein or clumping factor A or B), are at least 3 and less than 27 amino acids in length, or are specific for bacteria, viruses, or cancer cells. Some antigenic domains of ligand/receptor specificity exchangers comprise a peptide having an antibody-binding region of a pathogen or toxin, are at least 5 and less than 35 amino acids in length, or contain peptides that are obtained from polio virus, TT virus, hepatitis B virus, and herpes simplex virus. Despite these advances in medicine, there remains a need for more specificity exchangers that redirect antibodies present in an individual to a target molecule.